10 votes 10 votes What are the final values of $\text{Q}_1$ and $\text{Q}_0$ after $4$ clock cycles, if initial values are $00$ in the sequential circuit shown below: $11$ $01$ $10$ $00$ Digital Logic isro2014 digital-logic circuit-output ugcnetcse-dec2012-paper3 ugcnetcse-dec2013-paper3 + – focus _GATE asked Jul 17, 2015 edited Jan 15, 2023 by gatecse focus _GATE 12.4k views answer comment Share Follow See all 0 reply Please log in or register to add a comment.
Best answer 16 votes 16 votes Answer: (d) Explanation: T flip flop toggles the state if input T is 1, and does not change state if input T is 0. T flip flop is a clocked (synchronous or edge-triggered) flip flop. Edge triggered flip flops can only change its values at the edge of a clock, in absence of edge does not change its state, remains same. In given circuit, clock symbol is showing that it is positive edge triggering (low to high change). Note that there are mainly four different types of clock-triggering methods. Now, we need to find out Q0Q1 after 4 clock cycles.Initial: 00 States Q0 and Q1 are zeroClock 1: 11 State Q0 changed to 1 because input T is 1 and previous state was 0 and State Q1 changed to 1 because input T is 1 and previous state was 0.Clock 2: 01 State Q0 changed to 0 because input T is 1 and previous state was 1 and State Q1 remains same because clk value is 0.Clock 3: 10 State Q0 changed to 1 because input T is 1 and previous state was 0 and State Q1 changed to 0 because input T is 1 and previous state was 1.Clock 4: 00 State Q0 changed to 0 because input T is 1 and previous state was 1 and State Q1 remains same because clk value is 0. Mangilal Saraswat answered Jun 25, 2016 selected Jun 30, 2016 by Arjun Mangilal Saraswat comment Share Follow See all 2 Comments See all 2 2 Comments reply mcjoshi commented Sep 7, 2016 reply Follow Share Good explaination. 0 votes 0 votes Rams B commented Jun 2, 2018 reply Follow Share How is the sequence made? 0 votes 0 votes Please log in or register to add a comment.
7 votes 7 votes correct me if wrong! q0q1 (initial) 00 (1 clock) 10 (2 clock ) 01 (3 clock ) 11 ( 4 clock) 00 this will be answer............. focus _GATE answered Jul 17, 2015 focus _GATE comment Share Follow See all 15 Comments See all 15 15 Comments reply minal commented Aug 4, 2015 i edited by minal Aug 4, 2015 reply Follow Share no i think 11 will be the answer... 0 votes 0 votes focus _GATE commented Aug 4, 2015 reply Follow Share the sequence which i made is wrong or correct...?? 0 votes 0 votes minal commented Aug 4, 2015 reply Follow Share haa you did wrong.... 00 then 11 then 01 then 10 and again 00... 1 votes 1 votes minal commented Aug 4, 2015 reply Follow Share and if i consider q1 as MSB and q0 as LSB then it will be 00 -->11-->10-->01 -->00 so its mod 4 down counter . but in both cases after 4th clock it will be 11. 0 votes 0 votes Vivek sharma commented Aug 4, 2015 reply Follow Share it would be 00 not 11 becoz after 1 = 11 after 2 = 10 after 3 = 01 after 4 = 00 1 votes 1 votes minal commented Aug 4, 2015 reply Follow Share yes i got same sequence ... 00 -->11 -->10--->01-->00 but i confused after 4th clock means o/p or state ... but i have cleared ... by the way you assumed q1 as MSB naa 1 votes 1 votes Vivek sharma commented Aug 4, 2015 reply Follow Share Yup! 0 votes 0 votes minal commented Aug 5, 2015 reply Follow Share and if you consider q0 as MSB then what is seq,.. ? i just want to conform... 0 votes 0 votes Vivek sharma commented Aug 5, 2015 reply Follow Share if q0 is taken as MSB, sequence would be 00, 11, 01, 10, 00.......Again the ans would be 00. 0 votes 0 votes minal commented Aug 5, 2015 reply Follow Share okk ... i got same one ... but many didnt get same ...so i want to conform by the way thanks :) 1 votes 1 votes mathwalerp commented Jun 8, 2016 reply Follow Share The second flip flop is positive triggered. So I think it will never receive 1 as clock so it will not be activated.So output of second flip flop will be 0 and as 1 is supplied to first toggle flip flop it will always output 0.So answer should be 0. 0 votes 0 votes naga praveen commented Jun 12, 2016 reply Follow Share Could you please elaborate me on this . how output is being calculated in everystep 0 votes 0 votes Praveen Saini commented Jun 13, 2016 reply Follow Share @naga $Q_0$ is changing at each clock pulse and $Q_1$ is changing only when $Q_0$ changes from $0$ to $1$ 2 votes 2 votes naga praveen commented Jun 13, 2016 reply Follow Share Thanks Praveen 1 votes 1 votes Devwritt commented Jun 30, 2016 reply Follow Share it is a Asynchronous sequential circuit(because next ff clock depends on previous ff's output), so it will follow a sequence(like 00, 01 , 10 etc) so here sequence is q1 q0 initially, 0 0 clock 1- 0 1 clock 2- 1 0 clock 3- 1 1 clock 4- 0 0 1 votes 1 votes Please log in or register to add a comment.
1 votes 1 votes Sequential circuit would produce the following output: T0 Q0 T1 Q1 1 0 1 0 1 1 1 0 1 0 1 1 1 1 1 1 1 0 1 0 (Q0, Q1 = 0,0), after 4th cycle. So, option (D) is correct. IITB2020 answered May 25, 2020 IITB2020 comment Share Follow See all 0 reply Please log in or register to add a comment.